A conventional nail stapler includes a valve, a valve-opening rod, a trigger and a security element. The trigger must be pulled and the security element must be pressed against a piece of wood for example in order to push the valve-opening rod so as to open the valve. The valve-opening rod is pushed as long as the trigger is pulled and the security element is pressed, no matter which action is taken first. Hence, a user often pulls the trigger all the time and presses the security element against a piece of wood whenever he or she wants to shoot a nail. Thus, the security element becomes a de facto trigger. Moreover, every time the nail stapler shoots a nail at a spot, it vibrates. This vibration might cause the nail stapler to jump on the piece of wood. The user might immediately press the security element against the piece of wood because of inertia so as to shoot another nail at a spot very close to the previous spot. This wastes nails and damages the surface of the piece of wood.
Referring to FIGS. 9 to 12, a conventional single-shot nail stapler 67 includes a valve (not shown), a valve-opening rod 68, a major trigger 70, a security element 72, a spring 76 and a secondary trigger 60. The valve-opening rod 68 is movable. The major trigger 70 is pivotal. The security element 72 is movable. The major trigger 70 defines an aperture 74 through which the security element 72 extends.
Referring to FIGS. 13 and 14, the secondary trigger 60 includes a loop 62 formed at a first end and two branches 64 formed at a second end. A cutout 66 is defined between the branches 64.
Referring to FIG. 9, the spring 76 is compressed between an appropriate portion of the nail stapler 67 and the secondary trigger 60. A pin (not show) is forced into the major trigger 70 through the loop 62 so as to pivotally connect the major trigger 70 with the secondary trigger 60.
Referring to FIG. 10, the security element 72 is pressed so as to push the second end of the secondary trigger 60, thus bringing the secondary trigger 60 into contact with the valve-opening rod 68. Then, the major trigger 70 is pulled so as to move the loop 62, thus causing the secondary trigger 60 to push the valve-opening rod 68. Thus, the nail stapler 67 shoots a nail.
Referring to FIG. 11, the security element 72 is released while the major trigger 70 is still pulled. As biased by the spring 76, the secondary trigger 60 is pivoted about the pin. Thus, the second end of the secondary trigger 60 is moved beyond the security element 72.
Referring to FIG. 12, the security element 72 is pressed again and the major trigger 70 is still pulled. As the second end of the secondary trigger 60 is moved beyond the security element 72, the second end of the secondary trigger is not pushed by means of the security element 72. Hence, the valve-opening rod 68 is not pushed. Thus, the nail stapler 67 does not shoot another nail.
As mentioned above, the conventional single-shot nail stapler 67 can provide a single-shot function. However, it might fail to provide the single-shot function in at least two situations. Firstly, if the major trigger 70 is not pulled hard so that the second end of the secondary trigger 60 is not moved beyond the security element 72. Secondly, if the secondary trigger 60 is moved from its normal position so that one of the branches 64 abuts against the security element 72.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.